This invention relates to the synthesis of an aliphatic 1,3-diol, particularly 1,3-propanediol, from ethylene oxide and syngas in one step. More particularly this invention identifies a low cost bimetallic catalyst alternative that provides moderate yields under mild conditions in the one-step synthesis of 1,3-propanediol (1,3-PDO). The catalyst of the invention comprises a cobalt-iron catalyst, optionally in the presence of a ligand selected from N-heterocyclic, phosphine, or porphorine ligands, and optionally solubilized in an ether solvent.
Aliphatic 1,3-diols, particularly 1,3-propapediol, have many applications as monomer units for polyester and polyurethane, and as starting materials for the synthesis of cyclic compounds. For example, CORTERRA(copyright) polymer is a polyester characterized by outstanding properties that is made of 1,3-propanediol (hereafter 1,3-PDO) and terephthalic acid. There is much interest in the art in finding new routes for synthesizing 1,3-PDO that are efficient, economical, and demonstrate process advantages.
U.S. Pat. Nos. 3,463,819 and 3,456,017 teach the hydroformylation of ethylene oxide to produce 1,3-propanediol and 3-hydroxypropanal (hereafter 3-HPA) using a tertiary phosphine-modified cobalt carbonyl catalyst.
U. S. Pat. No. 5,304,691, assigned to Shell, discloses a method of hydroformylating ethylene oxide to 3-hydroxypropanal and 1,3-propanediol in a single step using an improved catalyst system comprising a cobalt-tertiary phosphine ligand in combination with a ruthenium catalyst. In ""691 1,3-PDO and 3-HPA are produced by intimately contacting an oxirane, particularly ethylene oxide (hereafter EO), a ditertiary phosphine-modified cobalt carbonyl catalyst, a ruthenium catalyst promoter, and syngas (carbon monoxide and hydrogen) in an inert reaction solvent at hydroformylation reaction conditions. A PDO yield of up to 86-87 mole % is reported, using a catalyst comprising cobalt ligated with 1,2-bis (9-phosphabicyclononyl)ethane as bidentate ligand, and either triruthenium(O) dodecacarbonyl or bis[ruthenium tricarbonyl dichloride] as cocatalyst.
The production of 1,3-PDO in one step with minimal impurities and byproducts involves recycle and requires a catalyst system with good stability both during 1,3-PDO synthesis and during product recovery and recycle. It would also be desirable if there were a low cost catalyst combination for the one-step synthesis of 1,3-PDO.
In accordance with the foregoing, the present invention provides an alternative to the use of known hydroformylation catalyst compositions in the one-step synthesis of 1,3-PDO. The invention is a homogeneous catalyst system comprising:
a) A cobalt component comprising one or more preferably non-ligated cobalt compounds; and
b) An iron component, optionally ligated with a ligand selected from a N-heterocycle, phosphine, or porphorine moiety.
It has surprisingly been found the bimetallic cobalt-iron catalyst, optionally ligated, is effective in the one-step synthesis of 1,3-PDO and therefore offers the advantage of a lower cost alternative. For example, dicobalt octacarbonyl in combination with iron pentacarbonyl, with N,N-dimethyldodecylamine as promoter, solubilized in 1,3-dioxolane has been demonstrated to exhibit moderate yields with minimal precipitate formation in hydroformylation (synthesis gas pressure conditions).
The novel oxirane hydroformylation catalyst of the present invention involves a complex which is postulated to be an cobalt: iron complex, alone, or optionally in combination with a ligand selected from a monodentate, bidentate or multidentate N-heterocyclic, a phosphine, or a porphorine. In this new bimetallic catalyst the ligand is believed to be predominantly attached to the iron rather than cobalt, as is the case in U.S. Pat. No. 5,304,691.
The invention also provides a one step process for preparing a 1,3-diol, comprising the reaction of an oxirane with syngas at hydroformylation conditions in an inert solvent in the presence of the catalyst complex of this invention.